Here we propose to develop an experimental paradigm to allow dynamic monitoring of the strength and location of every glutamatergic and GABA/Glycinergic synapse within the brain of a living organism. In combination with behavioral manipulation of the organism this paradigm will allow for study of how the brain encodes information in synaptic structure. This paradigm will involve combining three technologies: 1. Recombinant probes with which postsynaptic excitatory and inhibitory sites can be labeled in vivo, allowing the location and strength of synaptic connections to be monitored in parallel. 2. 2P-SPIM microscopy, which can image large volumes very quickly, without bleaching and, potentially, with isotropic resolution. 3. Software to calculate and store the location and strengt of each synapse in such a manner that it can be easily manipulated and analyzed. Experiments will be performed in zebrafish, as they have semi-transparent brains that are relatively small, yet they are capable of relatively complex behaviors. Experiments will be used both to establish the viability of the paradigm and to answer fundamental questions about how synapses are modulated during sleep, as well as how they are changed in learning paradigms such as sound habituation and place preference/aversion conditioning.